ENTOMOLOOY AND PLANT QUARANTINE 
41 
are present. In 1936 the average increase in yield of field-ciired peanuts from 
treated plots as compared with untreated rani?ed from 30 to e;0 percent. These 
results confirm those obtained in previous seasons. Although this leafhopper 
is resjwnsible for considerable loss in the yield of peanuts in Virginia and 
North Carolina, this increase in yield cannot be attributed solely to reduction 
in the leafhopper iwpulation. 
INSECTS ATTACKING SUGARCANE AND RICE 
Experiments conducted during the year gave preliminary information in- 
dicating that there is a much higher survival of the sugarcane borer in fields 
in which the cane trash is not burned than in fields in which such trash is 
destroyed by burning. This higher survival is apparently not compensated 
for by any increase in parasitization. 
It has been found that the green bug is a vector of mosaic disease of sugar- 
cane in Louisiana. 
The use of light traps has been found to be a method giving partial control 
of the sugarcane beetle. Certain varieties of cane were found to be more 
tolerant to attacks of this beetle than others. Repellents have given excellent 
results in protecting planted rice from attacks by this beetle. 
The West Indian cane fulgorid i Saccliarosydne saccharivora Westwood) was 
discovered for the first time in the United States causing heavy injury to some 
varieties of cane in Florida. 
It has been found that infestations of some of the worst insect pests of stored 
rice begin while the grain is still standing in the field. Rice grown near old 
stacks of rice straw was found to be 53 percent Infested while in the field. In 
preliminary work borax has been found of value in the control of stored-rice 
insects. When relatively small quantities are mixed with stored rough rice 
the development of the insects is prevented, and borax apparently has value in 
preventing the molding of rice having high moisture content when harvested. 
Investigations are in progress to determine whether the commercial use of 
borax in this way is feasible and safe, the size of the dose necessary, and the 
limits of applicability of the method. 
INSECTS ATTACKING STORED GRAIN PRODUCTS 
In a study of the distribution of fumigants in vacuum tanks, utilized for 
the control of insects attacking stored cereal products, it was found that when 
a tank is filled with merchandise capable of absorbing a fumigant, an equal 
distribution of the fumigant is not obtained, although theoretically a gaseous 
mixture when introduced into a nearly perfect vacuum should distribute itself 
uniformly throughout the tank. An excessive adsorption by the commodity 
near the gas inlet and adjoining free space occurs, so that by the time the 
fumigant has penetrated the product it is in a much more dilute form in 
the places reached last, and an incomplete and uneven distribution of mor- 
tality is olitained. It has been foimd that recirculation of the fumigant in 
the vacuum vault, for the first 15 minutes of exposure, is sufficient to give 
even distributi(»n and to produce the maximum effect obtainable by circulating 
the gas, and that a 25-percent reduction in the dosage is the maximum ol)- 
tainable by recirculation. It was found impractical to fimiigate floiu' and 
feeds with ethylene oxide-carbon dioxide mixture under vacuum when the 
temperature of the material fell below 70° F, At 85° (as in midsummer) the.se 
materials can be fumigated with dosages, per 100 pounds of material, of 5 
pounds of fumigant for 3 hours, 2 pounds for 6 hours, and IVj pounds overnight. 
At 70° a considerable increase in dosage is required. It was found that the 
susceptibility of insects to fumigants in vacuum fumigation increased as the 
pressure decreased and that this variation is due to differences in oxygen 
content of the tank rather than to pressure. The introduction of steam into 
vacuum tanks when the pi-essure registered 0.15 inch raised the temperature 
iniiformly throughout both the tank and its contents. A temperature of 122° 
maintained for 3 minutes mider these conditions killed several species of insects 
buried in wheat in a tank, including the resistant eggs of the confused Hour 
beetle. 
Claims have been made that heavier-than-air fumigants. such as chloropicrin 
and the carbon disulphide-carbon tetrachloride mixture, applied at the surface 
of grain bins in storage will penetrate effectively to the bottom of the bin. 
During the year it was shown by experiments, in which containers of insects 
were buried at each 15-foot level of a GO-foot bin, that these gases did not 
